1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly, to a wiring structure of a semiconductor device and a method for manufacturing the same.
2. Description of the Related Art
As semiconductor devices become more highly integrated or the speed thereof increases, a multi-layer wiring structure is required. Accordingly, it is important to secure an alignment margin in a photolithography process for reducing the pitch of metal wiring or succeeding wiring. It is necessary to increase the flatness of an insulating film for insulating the metal wiring in order to reduce the pitch of the metal wiring or to secure the alignment margin.
A process of planarizing the insulating film is necessary for increasing the flatness of the insulating film. For example, one such exemplary process comprises a method of forming an insulating film and polishing the insulating film globally by a chemical mechanical polishing (CMP) method. The process of planarizing the insulating film using the CMP method is essential for securing a processing margin and process stabilizing in manufacturing a multi-layer wiring structure.
FIG. 1 schematically shows a sectional view of the wiring structure of a conventional semiconductor device.
To be specific, the conventional wiring structure will be described, taking a static random access memory (SRAM) device in which the CMP method is used as a planarizing method, as an example. A first insulating film 31 insulates a lower structure such as a drain or source region 15 formed on a semiconductor substrate 10, a gate electrode 23, and a VCC line 40 from the metal wiring, for example, a first wiring 61. The first insulating film 31 is planarized by the CMP method in order to increase the flatness.
A groove of a second insulating film 35 formed on the first insulating film 31 is filled with the first wiring 61. Namely, the first wiring 61 is formed by a damascene process. A conductive stud 63 formed in a contact hole through the second insulating film 35 and the first insulating film 31 contacts the drain or source area 15. The first wiring 61 and the stud 63 are formed by filling the groove or the contact hole with a conductive film and polishing the conductive film by the CMP method. It is essential for securing the processing margin or the multi-layer wiring structure in a succeeding process to form the first wiring 61 or the conductive stud 63 by planarizing the conductive film by the CMP method.
However, the conductive film may be over polished when it is polished by the CMP method and the first wiring 61 or the conductive stud 63 can be excessively etched by this over polishing phenomenon. The first wiring 61 operates as a word line or a VSS line in the semiconductor device. Therefore, the excessive etching can reduce the cross sectional area of the first wiring 61, thus increasing the resistance of the first wiring 61 or cause a short of the first wiring 61. The increase of the resistance of the first wiring 61 can decrease the operating speed of the semiconductor device or cause misoperation of the semiconductor device. The conductive stud 63 is connected to second wiring formed on the first wiring 61.
To solve the above problem, it is an objective of the present invention to provide a wiring structure of a semiconductor device in which it is possible to prevent an increase in the resistance of the wiring or a short in the wiring by preventing the wiring from being excessively etched when a planarizing method such as a CMP method is used.
It is another objective of the present invention to provide a method for manufacturing the wiring structure of the semiconductor device by which it is possible to prevent the increase in the resistance of the wiring or the short in the wiring by preventing the wiring from being excessively etched when a planarizing method such as a CMP method is used.
Accordingly, to achieve the first objective, there is provided a wiring structure of a semiconductor device, comprising a body and a protrusion, formed of a conductive material in a first insulating film on a semiconductor substrate. The body is preferably a polygonal column or a hemispherical column. The protrusion is formed of a conductive material in a second insulating film formed on the first insulating film and connected to the upper surface of the body The protrusion is formed to have a width narrower than that of the body, and has a planarized upper surface.
The first insulating film is formed of a material having an etching rate greater than that of the second insulating film. A conductive stud insulated from the wiring by the first insulating film and the second insulating film, connected to the semiconductor substrate, and having a planarized surface having the same height as the planarized surface of the wiring is further comprised.
The conductive material is one selected from a group consisting of tungsten, aluminum, tungsten alloy, and aluminum alloy. The wiring structure can be applied to a semiconductor device such as an SRAM device. At this time, the wiring is used as a VSS line or a word line.
To achieve the second objective, there is provided a method for manufacturing the wiring structure of a semiconductor device. In the method, a first insulating film is formed on a semiconductor substrate. A second insulating film having an etching ratio less than that of the first insulating film is formed on the first insulating film. A second insulating film pattern having an aperture exposing some of the surface of the first insulating film is formed by patterning the second insulating film. A trench having a width greater than the width exposed by the aperture is formed by patterning some of the first insulating film exposed by the aperture. A conductive film for filling the trench and the aperture is formed on the second insulating film pattern. A protrusion and a body having a width greater than the width of the protrusion are respectively formed in the aperture and in the trench by planarizing the conductive film.
In forming the trench, a trench having a width greater than the width exposed by the aperture is formed by performing a dry etching or a wet etching process in a condition in which the etching rate of the first insulating film is greater than that of the second insulating film pattern. In forming the conductive film, the conductive film is preferably formed of a material selected from a group consisting of tungsten, aluminum, tungsten alloy, and aluminum alloy.
The forming of a contact hole exposing some of the semiconductor substrate by sequentially patterning the second insulating film pattern and the first insulating film is further comprised before forming the conductive film. The contact hole is filled together with the trench and the aperture in the step of forming the conductive film. A conductive stud is formed in the contact hole by planarizing the conductive film filling the contact hole in the planarizing of the conductive film. The conductive film is polished by a chemical mechanical polishing (CMP) method in the planarizing of the conductive film.
Such a wiring structure can be applied to a semiconductor device such as an SRAM device. At this time, the wiring is used as a VSS line or a word line.
According to the present invention, it is possible to prevent the excessive etching of the wiring and to pattern the wiring using a planarizing method such as the CMP method. Accordingly, it is possible to prevent the increase in the resistance of the wiring or the short in the wiring. Also, it is possible to use a multi-layer wiring structure, to secure a succeeding process margin, and stabilize a process.